Access point

ABSTRACT

An access point  10  providing a wireless LAN connection to a terminal device, for the purpose of connecting the terminal device to a WAN, the access point  10  includes: antenna units  210  and  310   a - d  that send and/or receive a radio frequency signal used for exchanging information via the wireless LAN; signal conversion units  220, 230, 240, 320   a - d,    330   a - d  and  340   a - d  that perform conversion between the radio frequency signal and a digital signal as the information; an information processing unit  110  that executes processing of the digital signal based on a communication protocol for exchanging of the information; antenna cases  200  and  300   a - d  that contain the antenna units and the signal conversion units; a main unit case  100  that, separated from the antenna cases, contains the information processing unit; and a wired cables  250  and  350   a - d  that, connecting the antenna cases and the main unit case, performs transmission the digital signal between the signal conversion units and the information processing unit.

BACKGROUND

1. Technical Field

The present invention relates to an access point of a wireless localarea network, and more specifically relates to a separate type accesspoint formed by a device main unit and an antenna unit using separatecases.

2. Related Art

A wireless local area network (hereafter called a wireless LAN) iscomposed from an access point that is a base station that is the centerof the wireless LAN and a terminal device that is a sub-station, andperforms the communication required between the devices that form thewireless LAN. As these access points, there are separate type accesspoints formed by a device main unit and an antenna unit using separatecases. An electrical connection is made between the device main unit andthe antenna unit using a wired cable. With this wired cable, sentsignals and received signals are transmitted between the device mainunit and the antenna unit. The separate type access point is used inlocations for controlling a wireless LAN, in cases when there is a fardistance with the location for providing this wireless LAN, and thelike. For example, to provide a wireless LAN to an outdoor terminaldevice, this separate type access point is widely used when the devicemain unit is installed indoors and the antenna unit is installedoutdoors.

Generally, electrical signals transmitted using wired cables undergoinsertion loss, and the signal level is attenuated. This insertion lossincreases relative to the cable length. For separate type access pointsas well, when the wired cable for connecting the device main unit andthe antenna unit is made longer, the insertion loss increases. Thisincrease in insertion loss is linked to a rise in the rate of datasending and receiving errors between wireless LAN devices, and therewere cases when it worsened the communication quality of wireless LANcommunication.

In the past, to suppress worsening of communication quality due to wiredcable insertion loss, there were access points equipped with opticalcables called optical fibers for the wired cable. This access pointconnected the device main unit and the antenna unit by an optical fiberwith low insertion loss, and performed transmission of radio frequency(hereafter RF) signals via this optical fiber. By doing this, it ispossible to reduce the insertion loss for the wired cable. Also proposedis an access point for which the device main unit is equipped with anamplifier for power amplifying the sent signals. This access point poweramplifies the sent RF signals transmitted by the wired cable. By doingthis, the sent signal insertion loss for the wired cable issupplemented. Similarly, to supplement the reduction of the receivedsignal loss, access points are also known that are equipped with anamplifier for amplifying the received signals at the antenna unit. Thisaccess point power amplifies the received RF signal transmitted usingthe wired cable. By doing this, the insertion loss of the receivedsignal with the wired cable is supplemented. As a result, these accesspoints are able to increase the communication quality of wireless LANcommunication.

As a reference for this part of the technology, there isJP-A-2002-325050. Noted in this reference is an access point for whichthe antenna unit is equipped with an amplifier for amplifying thereceived signals.

SUMMARY

However, these access points require optoelectronic conversioncomponents, amplifiers, or the like, or electrical control of these isrequired, which as a result invites the problem of making the deviceconstitution more complex, or the design more complex. Also, there isthe problem of the manufacturing cost increasing due to such things asspecial cable such as optical fiber being required, the number of partssuch as an amplifier increasing, and the man hours for assembly of theseincreasing.

An advantage of some aspects of the invention is to provide a separatetype access point that is able to increase the communication quality ofwireless LAN communication while trying to suppress an increase incomplexity of the device constitution, or to suppress manufacturingcosts.

A access point according to an aspect of the invention is an accesspoint providing a wireless local area network connection to a terminaldevice, for the purpose of connecting the terminal device to a wide areanetwork, the access point comprising: an antenna unit that sends and/orreceives a radio frequency signal used for exchanging information viathe wireless local area network; a signal conversion unit that performsconversion between the radio frequency signal and a digital signal asthe information; an information processing unit that executes processingof the digital signal based on a communication protocol for exchangingof the information; an antenna case that contains the antenna unit andthe signal conversion unit; a main unit case that, separated from theantenna case, contains the information processing unit; and a wiredcable that, connecting the antenna case and the main unit case, performstransmission the digital signal between the signal conversion unit andthe information processing unit.

According to this access point, the exchange of signals at the wiredcable between the device main unit and the antenna unit can be performedusing a digital transmission method. Generally, the digital transmissionmethod replays and transmits pulses for which the amplitude has beendecreased by insertion loss only by the pulse time position and thepresence or absence of the pulse, so it is possible to suppress thedegradation of signal quality more than with the analog transmissionmethod. As a result, it is possible to suppress a rise in the rate ofdata sending and receiving errors between wireless LAN devices.Furthermore, this access point is able to transmit digital signalshandled based on a wireless LAN communication protocol (e.g. IEEE 802.11or the like) using a wired cable. The wireless LAN devices are standardequipped with hardware for performing conversion and the like of analogsignal and digital signals and the like to execute processing based onthe wireless LAN devices. As a result, it is not necessary to separatelyprovide hardware for performing conversion of analog signals and digitalsignals and the like in order to perform digital transmission using awired cable. Therefore, it is possible to increase the communicationquality of wireless LAN communication while attempting to suppress anincrease in complexity of the device constitution or to suppress themanufacturing cost.

The access point of the invention having the constitution noted abovemay also use the following aspects. In accordance with an embodiment ofthe invention, the signal conversion unit may include: a frequencyconversion unit that performs conversion between the radio frequencysignal and an intermediate frequency signal having lower frequency thanthe radio frequency signal; a modem unit that performs modulation and/ordemodulation between the intermediate frequency signal and a base bandsignal; and a base band unit that performs conversion between the baseband signal and the digital signal.

In accordance with an embodiment of the invention, the transmission ofthe digital signal by the wired cable may be either one of serialtransmission and parallel transmission. With parallel transmission, itis possible to transmit digital signals in a group using a plurality oflines. By doing this, it is possible to increase the transmission speedof digital signals with a wired cable. Meanwhile, with serialtransmission, it is possible to transmit digital signals using one line.By doing this, skew does not occur in the signals between data lines, soit is possible to have more distance between the device main unit andthe antenna unit than in the case of parallel transmission.

In accordance with an embodiment of the invention, the wired cable, inaddition to transmission of the digital signal, may perform at least oneof transmission of a control signal and power supply, for at least oneof the antenna unit and the signal conversion unit. By doing this, it ispossible to connect with one set of wired cables between the device mainunit and the antenna unit. It is also not necessary to supply powerseparately to the antenna unit. As a result, it is possible to try tomake the access point installation work and maintenance work easier.

In accordance with an embodiment of the invention, the wired cable maybe coaxial cable. Coaxial cable has relatively strong resistance tonoise, so it is possible to set the device main unit and the antennaunit at a distance. Also, because this is less expensive than opticalcable, it is possible to suppress the manufacturing costs.

The aspects of the invention may also be referred to a method forexchanging signals at the access point. A method according to an aspectof the invention is a method for exchanging signals at an access pointproviding a wireless local area network connection to a terminal device,for the purpose of connecting the terminal device to a wide areanetwork, the method comprising: disposing an information processing unitin a main unit case, wherein the information processing unit executesprocessing of a digital signal based on a communication protocol used bythe wireless local area network; disposing a signal conversion unit inan antenna case separated from the main unit case, wherein the signalconversion unit performs conversion between the digital signal and aradio frequency signal which an antenna unit sends and/or receives overthe wireless local area network; connecting the main unit case and theantenna case via a wired cable; and transmitting the digital signalaccording to the protocol of the local area network via the wired cable.

With this method, it is possible to perform the exchange of signals viathe cable between the main unit case and the antenna case using digitalsignals according to the protocol of the local area network, to increasethe S/N ratio of the exchange of signals via the cable, and to reducethe communication error rate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram showing the overall schematicconstitution of an access point 10 for the first embodiment.

FIG. 2 is an explanatory diagram showing the internal hardwareconstitution of the access point 10 for the first embodiment.

FIG. 3 is an explanatory diagram showing the internal hardwareconstitution of an access point 11 for the second embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

In order to provide a clearer understanding of the constitution andadvantages of the invention, an access point embodying the presentinvention is described below.

First, the overall schematic constitution of the access point 10 for thefirst embodiment which is one aspect of the invention is described. FIG.1 is an explanatory drawing showing the overall schematic constitutionof the access point 10 of the first embodiment. The access point 10provides a wireless LAN at a service area 70 such as for a freeway. Inthe service area 70, there are regions in which vehicles such aspassenger cars, trucks, or the like park. The access point 10 providesthe wireless LAN terminal devices built into or brought to vehiclesparking in this region or to terminal devices within the service area 70such as installed terminal devices. Specifically, this wireless LAN isconstituted by the access point 10 and the terminal device within theservice area 70, the access point 10 provides a wireless LAN connectionenvironment to the terminal devices up to a specified number of unitsaccording to the connection capacity, and it is possible to providevarious different services such as internet access and the like via thewireless LAN to the connected terminal devices. These wireless LANdevices are wireless LAN devices compliant with the IEEE 802.11b and/or11g standards, which are wireless LAN standards.

The access point 10 is constituted by a main unit case 100 in which ishoused a device for mainly performing information processing for thewireless LAN communication or the like, a sending antenna case 200 inwhich is housed a device for handling sent signals for the wireless LANcommunication or the like, and four receiving antenna cases 300 a, 300b, 300 c, and 300 d in which are housed devices for handling receivedsignals for the wireless LAN communication. The main unit case 100 andthe sending antenna case 200 are connected by the coaxial cable 250. Themain unit case 100 and the receiving antenna cases 300 a, 300 b, 300 c,and 300 d are respectively connected by the coaxial cables 350 a, 350 b,350 c, and 350 d.

Considering the ease of system maintenance and weather resistance, themain unit case 100 is installed indoors in the control tower 75 providedtogether in the service area 70. The sending antenna case 200 isinstalled near the center of the service area 70 to be able to sendradio signals to terminal devices within the service area 70. Thereceiving antenna cases 300 a, 300 b, 300 c, and 300 d are installednear the respective four corners of the service area 70 to be able toreceive radio signals from the terminal devices within the service area70.

The access point 10 is connected to the internet 80 which is a wide areanetwork (hereafter called WAN). The access point 10 is able to performexchanging of information with other nodes connected to the internet 80via this connection. By doing this, the terminal devices within vehiclesparked within this service area 70 are connected to the internet 80 viathe access point 10, making possible internet communication forperforming exchanging of information with other nodes connected to theinternet 80. As aspects of this internet communication, there are webcontents acquisition, e-mail sending and receiving, internettelephoning, and the like.

Next, the hardware constitution inside the access point 10 for the firstembodiment is described. FIG. 2 is an explanatory drawing showing thehardware constitution inside the access point for the first embodiment.First, the hardware constitution inside the main unit case 100 isdescribed. Comprised in the main unit case 100 which constitutes theaccess point 10 are an information processing unit 110, a receivingsynthesis unit 120, a WAN communication unit 140, and an AP control unit130. The information processing unit 110 and the receiving synthesisunit 120 are electrically connected. Transfer of received digitalsignals to the information processing unit 110 is performed via thisconnection. The AP control unit 130 is connected to make possibleexchanging of information between the information processing unit 110and the WAN communication unit 140. By doing this, the informationprocessing unit 110 and the WAN communication unit 140 are able toperform mutual exchanging of information via the AP control 130. Bydoing this information exchange, it is possible to do communication viathe internet, and thus to realize information exchange.

The information processing unit 110 is also called a media accesscontroller (hereafter called MAC), and this is constituted by a one chipmicrocomputer comprising a CPU, ROM, RAM, various types of communicationinterfaces, and the like. This information processing unit 110 executesprocessing of digital signals which are information exchanged bywireless LAN communication based on a communication protocol compliantwith the IEEE 802.11b (or 11g) standard. The receiving synthesis unit120 is constituted by a one chip microcomputer comprising a CPU, ROM,RAM, various types of communication interfaces, and the like. Thisreceiving synthesis unit 120 performs diversity receiving byappropriately doing selective synthesis of an independent plurality ofreceived signals. By doing this, it is possible to reduce the phasingvariation and to suppress degradation of received signal quality. TheWAN communication unit 140 is constituted by a one chip micro computercomprising a CPU, ROM, RAM, various types of communication interfaces,and the like, and performs communication with the internet 80. The APcontrol unit 130 is constituted by a CPU, ROM, RAM, various types ofcommunication interfaces and the like, and performs various types ofcontrol on the access point 10.

Next, the hardware constitution within the sending antenna case 200 isdescribed. As shown in FIG. 2, the sending antenna case 200 thatconstitutes the access point 10 comprises a sending antenna 210, asending RF unit 220, a sending modulation unit 230, and a sending DAunit 240. The sending DA unit 240 is connected to the informationprocessing unit 110 comprised in the main unit case 100 via a coaxialcable 250. Furthermore, from upstream of the sent signal flow, there isan electrical connection in the sequence of the sending DA unit 240, thesending modulation unit 230, the sending RF unit 220, and the sendingantenna 210. Digital signals are output from the information processingunit 110 to the sending DA unit 240. The sending DA unit 240 convertsthe received digital signals to analog signals, and outputs these asbase band signals to the sending modulation unit 230. The sendingmodulation unit 230 modulates these base band signals using carrierwaves, and these are output as intermediate frequency (hereafter calledIF) signals to the sending RF unit 220. The sending RF unit 220 finallyconverts these to RF signals, and outputs them to the sending antenna210. Note that though omitted from the figure, each part of the sendingantenna case 200 receives various types of control signals from theinformation processing unit 110 via the coaxial cable 250 and receivessupply of power from the main unit case 100.

The sending DA unit 240 is constituted from a microcomputer that is alsocalled a base band processor. This sending DA unit 240 does D/Aconversion of sent digital signals sent via the coaxial cable 250 fromthe information processing unit 110, and converts these to base bandsignals for sending which are analog signals. The sending modulationunit 230 is constituted as a one chip processor comprising various typesof mixers, amps, filters, and the like for sending. This sendingmodulation unit 230 modulates base band signals for sending that wereconverted by the sending DA unit 240, and converts them to sent IFsignals. The sending RF unit 220 is a one chip processor comprisingvarious types of mixers, amps, filters, and the like for sending, andconverts the sent IF signals converted by the sending modulation unit230 to sent RF signals. The sending antenna 210 is a sleeve typenon-directional antenna comprising various types of amps, filters, andthe like. This sending antenna 210 emits the sent RF signals convertedby the sending RF unit 220 into space. By doing this, the access point10 is able to send wireless LAN communication information to theterminal devices within the service area 70.

Next, the hardware constitution inside the receiving antenna case 300 ais described. As shown in FIG. 2, comprised in the receiving antennacase 300 a that constitutes the access point 10 are a receiving antenna310 a, a receiving RF unit 320 a, a receiving demodulation unit 330 a,and a receiving AD unit 340 a. From upstream of the received signalflow, there is an electrical connection in the sequence of the receivingantenna 310 a, the receiving RF unit 320 a, the receiving demodulation330 a, and the receiving AD unit 340 a. Furthermore, the receiving ADunit 340 a is connected to the receiving synthesis unit 120 comprised inthe main unit case 100 via the coaxial cable 350 a. The RF signalsreceived by the receiving antenna 310 a are output from the receivingantenna 310 a to the receiving RF unit 320 a. The IF signals for whichRF signals were converted are output from the receiving RF unit 320 a tothe receiving demodulation unit 330 a. At the receiving demodulation 330a, detection demodulation is performed, and the base band signals areoutput to the receiving AD unit 340 a. The receiving AD unit 340 aconverts these to digital signals and outputs them to the receivingsynthesis unit 120. Note that the same as with the sending antenna case210, though omitted from the illustration, various types of controlsignals are sent to each part of the receiving antenna case 300 a fromthe receiving synthesis unit 120 via the coaxial cable 350 a, and supplyof power is also performed from the main unit case 100.

The receiving antenna 310 a is a flat diversity antenna comprisingvarious types of amps, filters, and the like. This receiving antenna 310a captures the wireless LAN communication radio waves in space andfetches them as received RF signals. The receiving RF unit 320 a is aone chip processor comprising various types of mixers, amps, filters andthe like for receiving. This receiving RF unit 320 a converts thereceived RF signals fetched by the receiving antenna 310 a to receivedIF signals in anticipation of detection demodulation. The receivingdemodulation unit 330 a is a one chip processor comprising various typesof mixers, amps, and filters for receiving. This receiving demodulationunit 330 a demodulates the received IF signals received from thereceiving RF unit 320 a, and outputs these as base band signals forreceiving. The receiving AD unit 340 a is a micro computer also called abase band processor. This receiving AD unit 340 a does A/D conversion ofthe base band signals for receiving fetched from the receivingdemodulation unit 330 a, and outputs these as received digital signals.These received digital signals are sent to the receiving synthesis unit120 via the coaxial cable 350 a. By doing this, the access point 10 isable to receive wireless LAN communication information from the terminaldevices within the service area 70.

The other receiving antenna cases 300 b, 300 c, and 300 d of the accesspoint 10 comprise the same constitution as the receiving antenna case300 a, so with FIG. 2, part of the illustration has been omitted. It isalso possible to receive wireless LAN communication information viathese receiving antenna cases 300 b, 300 c, and 300 d. Therefore, thereceiving synthesis unit 120 is able to receive received digital signalsfrom the coaxial cables 350 a, 350 b, 350 c, and 350 d. At this time,the data of the field intensity of the original RF signals forconverting to the received digital signals is received together. Thereceiving synthesis unit 120 selects the received digital signals withthe highest field intensity based on this data, and outputs the selectedsignals as wireless LAN communication received signals to theinformation processing unit 110.

According to the access point 10 of the first embodiment describedabove, the exchange of signals is performed via the coaxial cables 250,350 a, 350 b, 350 c, and 350 d between the main unit case 100, thesending antenna case 200, and the receiving antenna cases 300 a, 300 b,300 c, and 300 d using the digital transmission method. With thisembodiment, the maximum distance is 100 meters from the main unit case100 to the sending antenna case 200 or the receiving antenna cases 300 ato 300 d, but since the digital method is used for data exchange betweenthese, it is possible to increase the S/N ratio for sending andreceiving, making it possible to greatly reduce the sending andreceiving error rate. Therefore, it was possible to greatly reduce thedata sending and receiving error rate between the access point 10 andthe terminal devices. Finally, the access point 10 internally processesdigital signals based on IEEE 802.11b (or 11g), and with thisembodiment, these internal digital signals based on IEEE 802.11b (or11g) undergo power amplification, but for signal carrying, remain as isusing transmission via the coaxial cables 250, 350 a, 350 b, 350 c, and350 d. As a result, it is not necessary to separately provide hardwarefor performing conversion between analog signals and digital signals, orthe like. Therefore, it is possible to increase the communicationquality of wireless LAN communication while trying to suppress increasedcomplexity of the device constitution or to suppress manufacturingcosts.

In addition to the transmission of wireless LAN communication digitalsignals, the coaxial cables 250, 350 a, 350 b, 350 c, and 350 d are alsoused for transmission of various types of control signals from theinformation processing unit 110 and for supplying power from the mainunit case 100 side. Therefore, it is possible to connect between thedevice main unit and the antenna unit with one set of wired cables.Also, it is not necessary to separately supply power to the sendingantenna case 200 and the receiving antenna cases 300 a, 300 b, 300 c,and 300 d. As a result, it is possible try to make the access pointinstallation work and maintenance work easier.

Also, because the coaxial cables 250, 350 a, 350 b, 350 c, and 350 d arerelatively strong against noise, it is possible to make the distancebetween the device main unit and the antenna unit big at a scale of 100meters. Also, since it is inexpensive compared to optical cable, it isalso possible to suppress the manufacturing costs.

Next, the access point 11 of the second embodiment of the invention isdescribed. The access point 11 of the second embodiment differs from theaccess point 10 of the first embodiment in that it performs sending andreceiving of wireless LAN communication radio signals with a singleantenna. A typical illustration is shown in FIG. 3 of the hardwareconstitution within the access point 11 for this second embodiment. Asshown in the figure, the access point 11 comprises a main unit case 101for housing devices mainly for performing information processing forwireless LAN communication and the like, and an antenna case 201 forhousing devices for handling sent signals for wireless LAN communicationand the like. The main unit case 101 and the antenna case 201 areconnected by a coaxial cable 251. The main unit case 101 is installed inthe control tower 75, the same as with the first embodiment. The antennacase 201 is installed near the center of the service area 70 so as to beable to send and receive radio signals with the terminal devices withinthe service area 70. The coaxial cable 251 is installed in a form withmost of it buried underground. Note that it is also acceptable to have aplurality of the antenna cases 201 provided with these connected withthe main unit case 101 using a plurality of coaxial cables the same aswith the first embodiment.

Next, the hardware constitution within the access point 11 of the secondembodiment is described. First, the hardware constitution within themain unit case 101 is described. The access point 11 comprises in themain unit case 101 the information processing unit 111, the WANcommunication unit 140, and the AP control unit 130. For the hardwareconstitution within the main unit case 101, the information processingunit 111 differs from the first embodiment only in that the receiveddigital signals are directly received from the coaxial cable 251.

Next, the hardware constitution within the antenna case 201 isdescribed. The access point 11 comprises in the antenna case 201 theantenna 211, the RF conversion unit 221, the modem unit 231, and the ADconversion unit 241. From upstream of the received signal flow, theelectrical connection is made in the sequence of the antenna 211, RFconversion unit 221, modem unit 231, and AD conversion unit 241.Furthermore, the AD conversion unit 241 is connected with theinformation processing unit 111 comprised in the main unit case 101 viathe coaxial cable 251. RF signals are exchanged between the antenna 211and the RF conversion unit 221. The IF signals are exchanged between theRF conversion unit 221 and the modem unit 231. Base band signals areexchanged between the modem unit 231 and the AD conversion unit 241.Digital signals are exchanged between the AD conversion unit 241 and theinformation processing unit 111. Besides this, each part of the antennacase 201 receives various types of control signals from the informationprocessing unit 111 and receives supply of power from the main unit case101 via the coaxial cable 251.

The antenna 211 is a sleeve type non-directional antenna comprisingvarious types of amps, filters, and switches for switching radio wavesending and receiving and the like. This antenna 211 performs sendingand receiving of wireless LAN communication radio signals. The RFconversion unit 221 is a one chip processor comprising various types ofmixers, amps, filters and the like. This RF conversion unit 221 performsconversion between RF signals and IF signals. The modem unit 231 is aone chip processor comprising various types of mixers, amps, filters andthe like. This modem unit 231 performs conversion between IF signals andbase band signals. The AD conversion unit 241 is constituted by a microcomputer also called a base band processor. This AD conversion unit 241performs A/D conversion and D/A conversion, and performs conversionbetween base band and digital signals. The AD conversion unit 241performs exchanging of digital signals with the information processingunit 111 via the coaxial cable 251. This digital signal exchange isperformed using a half duplex communication method for switching betweensending and receiving. By doing this, it is possible to performexchanging of information via the wireless LAN between the access point11 and the terminal devices within the service area 70.

According to the access point 11 of the second embodiment describedabove, in addition to exhibiting the operating effect as that of thefirst embodiment, because sending and receiving of radio signals isperformed with a single antenna, it is possible to further simplify theoverall constitution.

Above, embodiments of the invention were described, but the invention isnot limited in any way to these kinds of embodiments, and it is ofcourse possible to implement various aspects within a scope that doesnot stray from the key points of the invention. For example,transmission of digital signals with wired cable may also be appliedregardless of whether this is serial transmission or paralleltransmission. Also, the wired cable is not limited to coaxial cable, butmay also be equilibrium shaped cable or the like. Also, the cable lengthis not limited to approximately 100 meters, but may also be a length ofapproximately 1 meter, or may exceed 100 meters. Also, the wireless LANprovided by the access point may be not wireless LAN communicationcompliant with the IEEE 802.11b standard of 11g standard, but ratheranother wireless LAN communication such as IEEE 802.11a or anotherwireless communication.

INDUSTRIAL APPLICABILITY

The invention may be used for a wireless LAN access point either indoorsor outdoors. Also, the location for providing the wireless LAN is notlimited to a service area such as of a freeway or the like, but may alsobe an amusement park, shopping mall, a sports stadium, an event site, aneducational institution such as a university, a factory, an office, orthe like.

1. An access point providing a wireless local area network operable toconnect a terminal device to a wide area network, the access pointcomprising: (a) an information processing unit operable to process adigital signal based on a communication protocol for communicating viathe wireless local area network; (b) a sending antenna case thatincludes: (i) a sending antenna and (ii) a sending signal conversionunit, without a function for receiving a radio frequency signal from theterminal device, wherein the sending signal conversion unit is operableto convert a digital signal from the information processing unit to aradio frequency signal for the wireless local area network, and thesending antenna is operable to send the converted radio frequency signalto the terminal device; (c) a plurality of receiving antenna casesspaced apart from the sending antenna case in a service area around thesending antenna case, wherein each one of the plurality of receivingantenna cases includes: (iii) a receiving antenna and (iv) a receivingsignal conversion unit, without a function for sending a radio frequencysignal to the terminal device, wherein each one of the receivingantennas is operable to receive a radio frequency signal from theterminal device when the terminal device is located between the sendingantenna case and the receiving antenna case, and wherein the receivingsignal conversion unit is operable to convert the radio frequency signalreceived from the terminal device to a digital signal for theinformation processing unit; (d) a main unit case that is separated fromthe sending antenna case and the plurality of receiving antenna cases,and includes the information processing unit and a receiving synthesisunit, wherein the receiving synthesis unit is operable to performdiversity receiving with respect to the received radio frequency signalsfrom the plurality of receiving antennas; (e) a sending wire cable thatconnects the main unit case to the sending antenna case to transmit thedigital signal from the information processing unit to the sendingsignal conversion unit; and (f) a plurality of receiving wire cablesoperable to transmit the digital signal from the plurality of receivingsignal conversion units to the receiving synthesis unit, wherein eachone of the plurality of receiving wire cables connects a respective oneof the plurality of receiving antenna cases to the main unit case.
 2. Anaccess point according to claim 1, wherein the signal conversion unitcomprises: a frequency conversion unit that performs conversion betweenthe radio frequency signal and an intermediate frequency signal havinglower frequency than the radio frequency signal; a modem unit thatperforms modulation and/or demodulation between the intermediatefrequency signal and a base band signal; and a base band unit thatperforms conversion between the base band signal and the digital signal.3. An access point according to claim 1, wherein the transmission of thedigital signal by the wired cable is either one of serial transmissionand parallel transmission.
 4. An access point according to claim 1,wherein the wired cable, in addition to transmission of the digitalsignal, performs at least one of transmission of a control signal andpower supply, for at least one of the antenna unit and the signalconversion unit.
 5. An access point according to claim 1, wherein thewired cable is coaxial cable.
 6. A method for exchanging signals at anaccess point operable to provide a wireless local area networkconnection to a terminal device, for connecting the terminal device to awide area network, the method comprising: disposing an informationprocessing unit in a main unit case, wherein the information processingunit is operable to process a digital signal based on a communicationprotocol used by the wireless local area network; disposing a sendingantenna case that includes a sending antenna and a sending signalconversion unit, without a function for receiving a radio frequencysignal from the terminal device, wherein the sending signal conversionunit is operable to convert a digital signal from the informationprocessing unit to a radio frequency signal for the wireless local areanetwork, and the sending antenna is operable to send the converted radiofrequency signal to the terminal device; (c) disposing a plurality ofreceiving antenna cases spaced apart from the sending antenna case in aservice area around the sending antenna case, wherein each one of theplurality of receiving antenna cases includes: (i) a receiving antennaand (ii) a receiving signal conversion unit, without a function forsending a radio frequency signal to the terminal device, wherein eachone of the receiving antennas is operable to receive a radio frequencysignal from the terminal device when the terminal device is locatedbetween the sending antenna case and the receiving antenna case; andwherein the receiving signal conversion unit is operable to convert theradio frequency signal received from the terminal device to a digitalsignal for the information processing unit; (d) disposing a main unitcase that is separated from the sending antenna case and the pluralityof receiving antenna cases, and includes the information processing unitand a receiving synthesis unit, wherein the receiving synthesis unit isoperable to perform diversity receiving with respect to the receivedradio frequency signals from the plurality of receiving antennas;connecting the main unit case and the sending antenna case via a sendingwired cable, connecting the main unit and each of the plurality ofreceiving antenna cases via a plurality of receiving wired cables,wherein a receiving synthesis unit in the main unit case is connected toeach one of the plurality of receiving antennas by a respective separatereceiving wired cable; and transmitting the digital signal according tothe protocol of the local area network via the wired cable.
 7. An accesspoint operable to effectively provide a wireless local network operableto connect a terminal device to a wide area network, the access pointcomprising: a main unit case that includes an information processingunit operable to process a digital signal based on a communicationprotocol for communicating with the terminal device; a sending antennacase separated from the main unit case, wherein the sending antenna unitcase, without a function for receiving a radio frequency signal from theterminal device, the sending antenna unit case includes a sending signalconversion unit and a sending antenna unit, wherein the sending signalconversion unit is operable to convert the digital signal from theinformation processing unit into a converted radio frequency signal forexchanging information via the wireless local area network, and whereinthe sending antenna unit is operable to send the converted radiofrequency to the terminal device; a plurality of receiving antenna casesspaced apart from the sending antenna case in a service area around thesending antenna case and separated from the main unit case, wherein eachof the plurality of receiving antenna cases is without a function forsending a radio frequency signal to the terminal device and eachreceiving antenna case includes a receiving antenna unit and a receivingconversion unit, wherein the receiving antenna unit operable to receivea radio frequency signal from the terminal device, and wherein thereceiving conversion unit operable to convert the radio frequency signalreceived by the receiving antenna unit into a digital signal fortransmitting to the information processing unit; a sending wired cablethat connects the main unit case to the sending antenna case to transmitthe digital signal from the information processing unit to the sendingsignal conversion unit; a plurality of receiving wired cables operableto transmit: the digital signal from each one of the plurality ofreceiving antenna cases to the main unit case wherein each one of theplurality of receiving wire cables connects one of the plurality of thereceiving antenna cases to the main unit case; and wherein theinformation processing unit includes a receiving synthesis unit thatperforms diversity receiving with respect to the radio frequency signalreceived at the plurality of receiving antenna cases.